We have a scenario where a user requests an "autonumber" for documents.

There is a field where they select the "document type" when adding a new item to the list, which is a lookup field (doc_type) held in another list call "Document_Types_Lookup".

The user could select one of up to 15 different document types when requesting a new item, and the autonumber should stay in sync with the document types…so there is no loss in the next available number for that particular document type.  This is why I can't simply use the ID column and append that to the "doc_type" field in a workflow.

Let's say we have the following autonumbers already in the list:
•DEMO-MATH-001
•DEMO-MATH-002
•DEMO-ENG-001
•DEMO-ENG-002
•DEMO-SCI-001

If a user submits a request for a MATH document, the number they should get to use is DEMO-MATH-003.

If a user submits a request for a SCI document, the number they should get to use is DEMO-SCI-002.

I have already used the autonumber in a workflow simply putting the ID column on the end, but this won't stay in sync with the particular doc type.

Thank you for any ideas!